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86 lines
2.4 KiB
86 lines
2.4 KiB
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/* Copyright 1998 by the Massachusetts Institute of Technology.
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*
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* Permission to use, copy, modify, and distribute this
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* software and its documentation for any purpose and without
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* fee is hereby granted, provided that the above copyright
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* notice appear in all copies and that both that copyright
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* notice and this permission notice appear in supporting
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* documentation, and that the name of M.I.T. not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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* M.I.T. makes no representations about the suitability of
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* this software for any purpose. It is provided "as is"
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* without express or implied warranty.
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*/
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#include "ares_setup.h"
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#include "ares.h"
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#include "ares_private.h"
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/* Routines for managing doubly-linked circular linked lists with a
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* dummy head.
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*/
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/* Initialize a new head node */
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void ares__init_list_head(struct list_node* head) {
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head->prev = head;
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head->next = head;
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head->data = NULL;
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}
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/* Initialize a list node */
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void ares__init_list_node(struct list_node* node, void* d) {
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node->prev = NULL;
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node->next = NULL;
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node->data = d;
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}
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/* Returns true iff the given list is empty */
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int ares__is_list_empty(struct list_node* head) {
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return ((head->next == head) && (head->prev == head));
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}
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/* Inserts new_node before old_node */
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void ares__insert_in_list(struct list_node* new_node,
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struct list_node* old_node) {
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new_node->next = old_node;
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new_node->prev = old_node->prev;
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old_node->prev->next = new_node;
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old_node->prev = new_node;
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}
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/* Removes the node from the list it's in, if any */
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void ares__remove_from_list(struct list_node* node) {
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if (node->next != NULL) {
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node->prev->next = node->next;
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node->next->prev = node->prev;
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node->prev = NULL;
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node->next = NULL;
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}
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}
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/* Swap the contents of two lists */
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void ares__swap_lists(struct list_node* head_a,
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struct list_node* head_b) {
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int is_a_empty = ares__is_list_empty(head_a);
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int is_b_empty = ares__is_list_empty(head_b);
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struct list_node old_a = *head_a;
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struct list_node old_b = *head_b;
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if (is_a_empty) {
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ares__init_list_head(head_b);
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} else {
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*head_b = old_a;
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old_a.next->prev = head_b;
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old_a.prev->next = head_b;
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}
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if (is_b_empty) {
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ares__init_list_head(head_a);
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} else {
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*head_a = old_b;
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old_b.next->prev = head_a;
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old_b.prev->next = head_a;
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}
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}
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